In such a known high-speed driving adapter, also called a high-speed milling spindle (see the magazine published by the firm Henninger KG, 7541 Straubenhardt, "High-Speed Milling Spindle", Type 817, September 1983), the gear housing includes a flange having in an outer surface a groove for engagement by a gripping arm of a tool changer. Furthermore, a pin which projects in an axial direction is provided on the flange and, during attachement of the high-speed driving adapter, engages a corresponding bore in the spindle housing and in this manner ensures that the gear housing is fixed against rotation with respect to the spindle housing. High-speed driving adapters basically step up the speed of the machine tool spindle by a factor of three to six, so that the boring or milling tool which is inserted into the tool-receiving spindle of the high-speed driving adapter rotates at a higher speed than the machine tool spindle. This known high-speed driving adapter can be automatically connected to and disconnected from the machine tool spindle by means of an automatic tool changer, but it does not permit an automatic exchange of boring or milling tools which can be inserted into the tool-receiving spindle of the adapter.
Furthermore, a tool chuck which is designed for installation in a machine tool spindle is known (see German magazine published by the firm Ott, "Reliable + Quick + Safe; Tool chuck", Nov. 4, 1982). This chuck can chuck and release tool taper shanks in the conical receiving bore of the machine tool spindle. This known tool chuck has for this purpose a collet carrier which is movably supported in a center bore of the spindle and is provided with a center ejecting pin and a collet, the collet having claws which can engage an annular groove provided at the free end of a tool taper shank. A cup-spring package urges the collet carrier in an axial direction. At the rear end of the machine tool spindle is a cylinder with a hydraulically actuable piston movable therein, which piston can move the collet against the spring pressure so as to release the collet and eject the tool taper shank. In particular, through the separately mounted cylinder, the known tool chuck has a very long structural length in an axial direction, which makes it impossible to store the tool chuck in this form in the relatively small space of a high-speed driving adapter.
A basic purpose of the invention is to provide, in a high-speed driving adapter or boring, milling and similar machine tools of the above-mentioned type, a chucking releasing and ejecting device of the type typically arranged in machine tool spindles, in order to make possible an automatic chucking, releasing and ejecting of the boring or milling tools which can be inserted into the high-speed driving adapter, but without substantially increasing the dimensions of the high-speed driving adapter. Moreover, the stability of the high-speed driving adapter, particularly thermal stability, is supposed to be improved.